Living Off the Grid, A Brief Introduction

by Caroline DiDomenico

In 2003, the idea of solar power and renewable energy had not been a new concept, but resources in Vermont to build your own off grid home required a lot of research, exploration, and getting to know the local grassroots experts.

It had been our intent to lessen our impact on the environment on land which was in a private wooded setting. Running power lines through our neighbor’s meadow was not an ideal situation for building friendships either. Alternative energy sources were explored and solar was selected after a local organization held green building tours at other Vermont homes.

The initial items purchased were a portable generator and gel batteries. This allowed for some small generation of power, that could be stored and run a few items at night, as well as provide power for tools necessary to continue to build.  We then added a small photovoltaic array, 3 150-watt panels, which powered the 6 12-volt batteries and kept them charged. Later, an additional 6 235-watt panels were added, and a new deep lead acid cycle battery storage system consisting of 12 2-volt batteries replaced the gel batteries. At this time another charge controller and new set of inverters were added as well.

The house was built in phases, and until 2017, the power system was designed only for weekend use and was shut down prior to leaving. 

Some quick basics on what components are needed for an off grid solar power system:

Photovoltaic Solar Panels – your source of power

Charge Controller – used to safely charge and protect the batteries from overcharging

Inverter – Your inverter converts DC to AC

Solar panels deliver, and batteries operate with Direct Current (DC)

Standard outlets provide power in Alternating Current (AC)

Batteries – Your energy storage bank—use it carefully!

Generator - Your back up power source (usually a necessity)

The current upgrade to the system, operational in 2018, was designed with the intent of making the house suitable for full time occupancy. In order to do this, we determined we wanted to have 4-5 days of autonomy (no sun at all to recharge the batteries, and no use of generator). Think worst case scenario of winter storms in Vermont; we sized the battery bank for this. The bank consists of 24 2-volt 1000 amp-hour batteries, to make a 48-volt, 48,000 amp-hour battery system. From this, we determined we’d need a13.5 kW PV array. Now we need to manage all that power coming into the batteries; this is where the charge controllers come in. We chose charge controllers that could all communicate to one another. 6 of the original PV panels are wired to one controller, then the new ground array was wired in 3 separate sections to 3 other controllers, with a 5th controller for 3 new panels on the south wall of the house. The system allows for one controller to take charge if another isn’t producing as much power, and continuously provide maximum energy to the batteries.

When we designed the system for full time use, we accounted for all the present day and future power loads we would like to have in place; the result was a 6.8 kW 240-volt inverter (that also communicates with the PV controllers).  The entire system performance and status is continuously available via an Android phone app.

The ground array today has room to expand, and we currently have more power than we need right now.

As we explore future plans for the house, we would like to consider a small turbine as an option, but this would be done only when the house is occupied full time. Wind power can produce an excess of power at any given time and you need to be able to have a place to dump the extra load or be able to shut the system down completely to protect the turbine from damage.

One day, our hope is to be able to have the entire house power needs, including heat, be produced via 100% renewable power!

System Block Diagram (Simplified)

Controllers and Inverter, Battery Box below, normally left open

New ground array with room for expansion                             

New array and original array on pole barn

Panels are mounted on side of house to allow for continuous “trickle charge”. There is little opportunity for snow and ice to remain on these, ensuring the batteries are always receiving a charge even in the worst weather.

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